US2157115A - Muffler - Google Patents

Description

May 9, 1939.

E. s. coRNELL, .JR

MUFFLER Filed Aug. l1, 1957 l amv-ranas. i

vllNvraln-OR Y Edward 5. come) ,Jr.

Hs/ O EY Ila) Patented May 9, 1939 UNITED STATES ruins PATENT OFFIQE MUFFLER Application August 11, 1937, Serial No. 158,484

4 Claims.

This invention relates to sound deadening devices.

More particularly, the invention relates to means for muflling sounds generated by vibrations set up Within a fluid-driven turbine or motor, by the siren effect of the interruptions to the iiow of the driving fluid by the reacting blades or buckets of the rotor or by other causes. The resulting sound waves are borne into the open on the column of spent driving fluid, and are thus audible to those in the vicinity of the motor.

The invention finds particular application With the Air conditioned heating and cooling system described and claimed in my United States Patent No. 2,033,347, granted April 21, 1936; said system including a unit comprising a heat exchanger over which compressed air, preferably pre-conditioned, is blown by a fan actuated by a prime-mover deriving its motive power from the pre-conditioned air suitably compressed; the conditioned air discharged by each motor being projected by the fan across the heat exchanger.

As such air conditioning units are primarily intended for service Within a closed room, it is desirable to quiet sounds incident to and resulting from their operation to as great an extent as is practicable.

This invention provides an air-motor-exhaust muflier which permits the substantially free flow of the discharged, conditioned air from the motor casing, and thus minimizes the creation of backpressures Within the motor casing. Additionally and incidentally, the mufller provides for filtering the air stream prior to its distribution by the fan.

In this invention, there is employed a mass of acoustically absorbent material having a central bore providing for the continuous and substantia-ily unobstructed passage of the air discharging from the motor. The acoustic mass is preferably a self-supporting cylinder` housed Within suitable metallic tube having a screw-threaded inlet port and a removable cap provided with a suitable discharge orifice. To diffuse and set up turbulences in the air column at its entry to the sound-absorbing cylinder, thus acting to reduce the columnar effect of the air column and bring the vibrating air stream into intimate contact with the acoustically absorbent mass, there is provided a disc of suitable resilient, porous material at the inlet port of the muffler. There may also be provided a similar disc at the outlet port; the discs additionally and incidentally serve as filtering means and as resilient and shock-absorbing inserts between the absorbent mass and the capped ends of the housing.

O'ther features and advantages will hereinafter appear.

In the accompanying drawing:

Fig. l is a representation of a heat exchangev unit as disclosed in the aforementioned United 'v States Patent, the fan-motor discharge of the unit being provided with my improved muffler;

Fig. 2 is a vertical section taken through the mulller on an enlarged scale; and l Fig. 3 is a horizontal section taken on the line" 3 3 of Fig. 2.

Referring to Fig. 1, an air conditioning system includes a thermal exchange unit I ll comprising headers I I and I2, arranged to distribute a heating or cooling medium through the passages of the radiator I3. An inlet connection I4 and an outlet connection I5 are provided for connection with the necessary piping of the central heating or cooling system, not shown.

Compressed conditioned air, that is, air which' has been cleaned, humidied and compressed at a central point, is made available for thermal treatment by the exchanger through the conduit l5, which taps the compressed conditioned-air supply. The conditioned air, prior to its release into the diffusion casing or mounting II, is caused to operate an air-motordriven fan I8, which blows the volume of conditioned air through the radiator I3 and thus eiects a rapid and efii cient heat interchange.

The fan I8 is driven by an air motor I9, preferably of the type described and claimed in my United States Patent #1,926,528, granted September 12, 1933, and entitled Air motor. As stated, the motor is actuated by the supply of compressed air, introduced into the motor through conduit 2li, and discharged therefrom, preferably behind the fan I8, through orifice 2|. A suitable control valve 22 may be provided as a means of regulating the speed of the motor and volume of air discharge.

To muille or substantially eliminate those sound-generating vibrations originating within the motor and carried from Within the motor casing on the column of discharged air, I provide an efficient and novel muler.

Referring to Fig. 2, the muffler 30 includes casing 3l, preferably a brass or otherwise suitable metal tube of proper length. A screw-threaded inlet port or base 32 may be permanently aixed to the tube, and a plug or cap 33 removably secured thereto, as by the threaded connection illustrated in the figure. The ports 32a, 33a of the respective fittings are of suitable diameter to accommodate the air ow. Within the casing, I provide a removable cylindrical filler 34 of sound deadening and acoustically absorbent material, such as preformed asbestos felt, cellulosic fibre, glass wool or the like. Preferably the said filler is in self-sustaining cylindrical or cartridge form, having an uninterrupted passage Sila therethrough which may be equal in diameter to the diameter of the ports 32a, 33a, and is in register therewith. T he wall of the passage 34a is entirely unconfined. The ller 34 preferably rests upon, and is capped by, resilient, porous discs 35, 36, the structure of which offers but slight resistance to the air flow. Soft felt has been found satisfactory for the said discs. rihe disc 35 serves to diffuse and set up turbulences in the air stream at its entry into the muffler, thus breaking up the columnar characteristic of the discharging air, and bringing the vibration-laden stream into intimate contact with the surface of the filler 34. In concert, the discs 35, 36 insulate the outer casing 3| from vibrations induced Within the muffler, serve as air filtering means, and additionally act as cushioning members for the protection of the sound absorbent ller.

The muffler is preferably attached directly to the exhaust 2i, as indicated in Fig'. 1; the threaded nipple 32h cooperating with suitable female threading of the exhaust. As shown, the outlet 33a of the muler is disposed relatively to the concave inner wall of the casing l1, which thereby directs the discharged air downwardly and into the path of the fan-induced air-stream.

The filler 34 is preferably odorless and nonabsorbent of odors, to insure that the air may not be contaminated or otherwise affected by contact therewith.

According to accepted scientific principles, the sound deadening effect of the muffler may be considered to be derived from the viscous resistance which the porous wall surface of the filler offers to the air-borne sound Waves, and also to the additional loss of energy of the sound waves, as they set in vibration the minute fibers of the ller material.

It will be seen that, except for the slight resistance offered by the discs 35, 36, the passage of the air through the muffler is substantially unrestricted. Efficient muliling is thereby accomplished with a minimum back pressure.

Whereas I have described my invention by reference to specific forms thereof, it will be understood that many changes and modifications may be made without departing from the spirit of the invention.

I claim:

l. A muier for silencing the discharge from an air motor or the like comprising, in combination, an outer shell, a cylindrical lining of soundabsorbinfr material contained within said shell, said cylindrical lining having an axial passage affording continuous and substantially unrestricted flow of discharge gas therethrough, closure means arranged to cap the ends of said shell, said closures being provided with inlet and outlet ports in register with said axial passage, and porous cushion means interposed between said cylinder and the said top and bottom closures, said cushion means disposed directly in the path of gas flow and arranged to create turbulences in said gas flow during passage thereof through said muffler.

2. A muffler for silencing the discharge from an air motor or the like, comprising, in combination, an outer shell, a self-supporting cylindrical lining of sound-absorbing material contained within said shell, said cylindrical lining having an axial passage affording continuous and substantially unrestricted flow of gas therethrough, the entire wall of said passage being exposed to direct contact with the ow of gas, closure means arranged to cap the ends of said shell, said closures being provided with gas inlet and discharge ports in register with said axial passage, and porous cushion means interposed between said cylinder and the said top and bottom closures, said cushion means disposed directly in the path of gas flow and arranged to create turbulences in said gas flow during its passage through said muffler.

3. A muffler for silencing the discharge of an air motor or the like, comprising, in combination, an Outer shell, a self-supporting cylindrical lining of soundabsorbing material contained within said shell, said cylindrical lining having an axial passage affording continuous and substantially unrestricted flow of gas therethrough, and presenting an unconned surface of said sound-absorbing material throughout its entire length, closure means arranged to capthe ends of said shell, said closures being provided with gas inlet and discharge ports in register with said axial passage, and resilient fibrous means interposed between said sound-absorbing cylinder and said bottom closure and arranged to effect an initial sound absorption and to set up turbulences in the gas stream prior to the contact of said stream with the surface of said axial passage.

4. A muier for silencing the discharge of an air motor or the like, comprising, in combination, an outer shell, a self-supporting cylindrical lining of sound-absorbing material contained within said shell, said sound-absorbing cylinder having an axial passage having a wholly unconned surface, and affording continuous, substantially unrestricted and uni-directional flow of gas through said muffler, top and bottom closure means for said shell, said closure means having inlet and discharge ports in register with said axial passage, and flow-permitting cushion means interposed between said cylinder and the said top and bottom closures, said cushion means directly intercepting the path of gas ow and arranged to set up turbulences in the gas stream during its ow through said axial passage, said cylindrical lining having its complete inner surface in direct contact with said gas flow.

EDWARD S. CORNELL, JR.

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